Tilting molten metal dispenser with constant liquid head control

ABSTRACT

Apparatus for metering an exact charge of molten metal, particularly magnesium, into the pressure chamber of a die casting machine which comprises automatically maintaining a constant head of metal over the discharge opening of the device by use of a weight responsive spring which tilts the reservoir as the charge of metal decreases.

Bauer m1 3,856,183 [451 Dem-24, '1974 'IILTING MOLTEN METAL DISPENSER wrru CONSTANT LIQUID HEAD CONTROL Alfred F. Bauer, Toledo, Ohio Waddington et al 222/106 UX 3,439,759 4/1969 Rouanet et al. 177/! 3,456,713 7/l969 Michelson 3,718,175 2 1973 Rinesch'. 164/281 x [75] Inventor: V

[73] Assignee: NL Industries, lnc., New York, NY. j 'f 2 f lg iiyg s g g i g 'sszstant xammer av1 c er e [22] Fled: I974 g Attorney, Agent, or FirmOwen & Owen [21] Appl. No.: 454,242 a u I 57] ABSTRACT.

2% g i g3 Apparatus for metering an exact charge of molten DIG 9 64 metal, particularly magnesium, into the pressure "222 16Z T6g- P- 7O 77 2 3 3 chamber ofadie casting machine which comprises au-- l 1 l tomatically maintaining a constant head of metal over the discharge opening of the device by use of a'weight 'responsive spring which tilts the reservoir as the [56] uNlTE g s g x i E s giiENTs charge of metal decreases. 2,088,547 7/1937 Camerota. 222/166 4 p wl Figures 7 H 3'7Ji 'A .23 7 a 77m 1 11 1 1 W I l 34 "74- 1 f -24 l i e 1m la/ I 1 1 fii 2 .//7 1 A, 13 \'1 'T 1 w l ;1;: l I V 42 M I 2/ I l t 1 l 1' w /2 4L i: I A; /9 (r v r 4/ l ls e4 1 Y .P ATENTEU DEC24 I974 sum 1 gr 3 PATENTE D DEC 2 4 I974 sum 2 0r 3 PATENTEI] DEC 24 I974 sum 3 o 3 llll TILTING MOLTEN METAL DISPENSER WITH CONSTANT LIQUID HEAD CONTROL BACKGROUND OF THE INVENTION The metering of an exact charge of molten metal, particularly magnesium, into'the pressure chamber of a cold chamber die casting machine without exposing the metal to the oxidizing influence of the air-prior to its discharge from the metering device has presented over the years a troublesome problem for the die casting industry. I I

' Magnesium has excellent die casting characteristics but it has not been as widely used in the industry as has aluminum largely because no well functioning, low cost metering device has yet been developed for discharging charges of magnesium into a die casting machine.

Many such metering devices have been proposed. The

failure to close tightly against their seats. Inaddition, I

the metal in any discharge pipe between the metering device and the shotsleeve of a cold chamber die casting machine may be subject to oxidation (by air entering the pipe) and/or deposits which prevent an even and controlled flow through the pipe.

Furthermore, the quantity of metal metered out on each cycle depends'on the metal volume in the holding pot. Float systems to control the metal level do not work well because oxides of the flux commonly used and dirt deposits build up on the floating device making it completely inoperative. Electric sensing devices to determine the level of the metal in the pot have commonly used highvoltagesparks but these have not been effective and accurate enough because of the build up of dirt and oxide particles between the actual surface of the metal and the electrodes through which sparking is intended to take place.

BRIEF DESCRIPTION OF THE INVENTION.

The present invention overcomes most of the shortcomings of known metering systems for magnesium. The molten magnesium is poured into a chamber which has no pump and which has no pipe extending between the holding vessel in which the magnesium is contained and the pouring opening of the shot sleeve of the die Since the tilting device does not come in contact with molten metal it will function without interruption and in a constant manner.

The holding pot is shaped so that the metal surface area remains in the-same size and shape throughout the 2 range of operation of the machine and in this way the protective film which forms on the'surface of the metal within the pot is not disturbed or broken as metal is extracted therefrom and poured into the die casting machine. I y I By tilting the holding pot into a particularly low position,.the valveseat which normally'stops off the opening in the holding pot becomes exposed which enableseasy replacement of the valve and repair of the valve seat without'emptying the holding pot. The holding pot is so shaped as to facilitatecleaning out sludge that accumulates on the bottom during normal operation.

BRIEF DESCRIPTION OF THE DRAWINGS I FIG. 1 is a side elevational and central vertical sectional view of an apparatus constructed in accordance with the present invention, with an extreme operating v positionshown in dotted lines;

FIG. 2 is a top plan view thereof;

FIG. 3 is an end elevational view thereof; and

FIGS. 4 and 5 are sectional views through the discharge. opening, with a preferred form of discharge valve being shown in full lines in its'open and seated positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment 'of the invention is shown in the drawings in which a cart 10, mounted on a series of wheels 11, carries the entire mechanism as a unit so that it'may be wheeled into and out of association with a die casting machine. The shot sleeve of a die casting casting machine. The metal enters the shot sleeve cludes a holding pot or crucible 15 that has a shallow end 15a and a deep end 1512. The bottom of the holding pot 15 between the deep and shallow ends is substantially a straight line. Adjacent the shallow end the holding pot is pivoted on trunions 16 between the arms 14. At its rear end the holding pot is supported on a frame 17 that engages spaced operating members 18, the lower end of each of which is pressed upwardly'by a spring 19 between the member and a pivoted plate 20 mounted on the cart 10. In the preferred form, as. shown in FIG. 3, the springs and operating members on each side of the rear of the holding pot are spaced outside the lateral dimemsions of the pot 15.

The frame 17 is pivotally attached to a link 21 which, in turn, is pivotally attached-at its'upper end to rod 22 received in spaced arms 23 carried by the pot 15.

The top of the pot 15 has a tightly fitting removable.

cover 24 by which access to the interior may be established for cleaning.

The springs 19 provide the simplest form of a weight Y sensing device so that, if the holding pot 15 is full of tained throughout the operating range of the metering tion prior to refilling. Weight responsive actuating de vices are known in the art (see Rouanet et al US. Pat. No. 3,439,759) and any of-these may be used in place of the simple springs 19. j I

At the shallow end, and at a point brought directly over the pouring opening 13 of the shot sleeve 12 a discharge opening 30 is formed in the lower wall of the shallow end of the holding pot. The discharge opening will be described im more detail later. The discharge opening is closed, preferably, by a simple reciprocating valve 31 operated by an air cylinder 32 and the entire mechanism is carried by a, yoke 33 mounted on the frame of the machine by any suitable devices such as posts 34, Replacement of the valve'31 and cleaning of v the valve seat 30 becomes a very simple matter if the yoke 33 is removed from the posts 34 because the valve can be removed upwardly from the holding pot and exposed for cleaning. Furthenat this time, the support interior thereof and the removal of any sludge that may springs 19. When a suitable charge has been introduced to place the metal level at about the level 25 the cart and the entire device is moved into registry with the die casting machine so that the discharge opening 30 is directly over the pouring opening 13 of the shot sleeve of the die casting machine. Thereafter, casting operation can proceed in a normal manner with the valve 31 rod 22 can be disengaged from the arms 23 and the entire pot lowered to expose the valve seat 30 without re- I moving the. contents of the pot. In general, the valveseat 30 requires only a cleaning operation and seldom requires renewal. 1 v At the rear of the holding pot 15 there is a replace- I able filling spout 36, carried by the cover 24 of the pot and shields the interior of the pot against the entry of air. Metal introduced through the opening 38 enters theinterior of the pot 15 without creating excessive turbulence except in the area adjacent the filling spout.

With the holding pot in its normal position the metal lever 25 stands at a preselected distance above the 'discharge opening 30 to provide a given head of molten metal over the discharge opening. It will be seen that the entire unit is lifted by the springs or lowered by the weight of the metal charge and that since the trunions 16 are adjacent the discharge, opening 30 a constant metal head is maintained above the discharge opening 30. Since the metal charge metered out at each opening of the valve 31 depends on fixed factors such as the diameter of the discharge opening 30 and the time of opening of the valve 31, which may be timed repetitively by operation of the air cylinder 32, the principal variable determining the metal charge metered into the die casting machine is the head of metal above the discharge opening. The present invention, therefore, eliminates this variable by maintaining, over a wide range, a constant head of metal above the discharge opening 30.

Any suitable clean-out opening may be provided in the cover 24 of the holding pot for easy access to the The temperature of the metal within the holding pot J ervoir to a point of use comprising opened and closed periodically by the air cylinder 32 with the assurance that the same charge of metal will enter the pouring opening 13 at each timed and equal reciprocation of the valve 31. The metal level will be maintained because, as above noted, the pot becomes ligher as the metal is discharged therefrom and the rear of the pot is moved upwardly by the springs 19 about the trunions 16. Any suitable alarm or indicating mechanism may be used in conjunction with the device to indicate to the operator when the metal charge has been reduced to such a point that it must be renewed because the pot has reached the tilted position approximately that of the dotted lines in FIG. 1. Thereafter, further tilting would not be advisable because of the possibility of sludge entering the discharge opening. Several hundred pounds of metal can be cast before it is necessary to renew the charge and charge renewal is relatively simple because of the remote location of the filling opening 38 from the die casting machine itselt:

What I claim is: 1. A device for metering charges of metal from a reservoir to a point of use comprising 7 a metal supply pot, pivot means adjacent one pivot point. t I a discharge valve having a valve seat in the lower wall of said supply pot close to said pivot point, said lower wall extending downwardly and away from said discharge valve, means to support said supply pot for tilting movement around said pivot point to maintain a substantially constant head of molten metal over said discharge valve seat, and means to open said discharge valve for a predetermined time period whereby substantially equal charges of metal flow through said discharge seat at each valve'opening. v 2. A device in accordance with claim 1 in which said means to support said supply pot is releasable so that said supply pot may be swung downwardly to expose said discharge valve seat for servicing.

3. A device for metering charges of metal from end of said pot defining a a metal supply pot, v

pivot means adjacent one end of said pot defining a pivot point. v

a discharge valve having a valve seat in the lower wall of said supply pot close to said pivot point.

said lower wall extendingdownwardly and away from said discharge valve,

weight responsive means to support said supply pot for tilting movement at a point removed from said charges of metal flow through said dischargeseat at each valve opening. 4. A device in accordance with claim 3 in which said 5 weight responsive means comprises at least one spring. 

1. A device for metering charges of metal from a reservoir to a point of use comprising a metal supply pot, pivot means adjacent one end of said pot defining a pivot point. a discharge valve having a valve seat in the lower wall of said supply pot close to said pivot point, said lower wall extending downwardly and away from said discharge valve, means to support said supply pot for tilting movement around said pivot point to maintain a substantially constant head of molten metal over said discharge valve seat, and means to open said discharge valve for a predetermined time period whereby substantially equal charges of metal flow through said discharge seat at each valve opening.
 2. A device in accordance with claim 1 in which said means to support said supply pot is releasable so that said supply pot may be swung downwardly to expose said discharge valve seat for servicing.
 3. A device for metering charges of metal from a reservoir to a point of use comprising a metal supply pot, pivot means adjacent one end of said pot defining a pivot point. a discharge valve having a valve seat in the lower wall of said supply pot close to said pivot point, said lower wall extending downwardly and away from said discharge valve, weight responsive means to support said supply pot for tilting movement at a point removed from said pivot point, said weight responsive means acting to tilt said supply pot around said pivot point to maintain a substantially constant head of molten metal over said discharge valve seat, and means to open said discharge valve for a predetermined time period whereby substantially equal charges of metal flow through said discharge seat at each valve opening.
 4. A device in accordance with claim 3 in which said weight responsive means comprises at least one spring. 